This invention relates generally to optical pellicles, and more particularly to a holder for such a pellicle.
Pellicles have played an important role in the fabrication in semiconductor wafers used in integrated semiconductor circuits. As is perhaps best described in U.S. Pat. No. 4,131,363 to Shea et al., an optical pellicle is comprised of a thin transparent membrane which is stretched over a rigid pellicle frame. The pellicle is placed directly onto a photomask such that the membrane is positioned at a distance spaced from the mask. Thus, smaller particulate and dust which falls onto the pellicle membrane is out of focus during the photolithography process, and will not therefore be reproduced in the silicon wafer.
To fabricate a pellicle, a very thin membrane, normally in the range of 0.50 to 3.0 microns, is first formed on a substrate. The membrane is then removed and mounted to a frame on which it is sold. Pellicle frames take many shapes, depending upon the photolithography equipment with which the pellicle is ultimately to be used. After fabrication has been completed, an extensive inspection process takes place. During this inspection process, the pellicle is manually handled and is mounted to various types of inspection machinery. Once inspection has been completed, the pellicle is packaged, in a package such as that described in my U.S. Pat. No. 4,470,508. This package includes shoulders to properly hold the pellicle in place, and typically has an exposed adhesive or piece of double-sided tape to collect any contaminants which might be floating in the air within the package. When the pellicle is to be used, it is manually removed from the package and mounted directly to the photomask with which it is to be used.
While the use of my patented package has been effective in preventing contamination of the pellicle during shipping, because the pellicle must be handled during inspection and mounting to the photomask, there remains a very real possibility of contamination and/or damage to the pellicle membrane during these procedures.
It is therefore a general object of the present invention to provide a system for handling pellicles which overcomes the drawbacks and limitations of prior art proposals. More specifically, the invention has as its objects the following: (1) to provide an optical pellicle handling system which reduces the likelihood of contamination or damage to the pellicle membrane; (2) to develop a holder for an optical pellicle, in which the pellicle can be mounted during fabrication to the inspection processes and reduce direct handling of the pellicle; (3) the provision of a pellicle holder which holds the optical pellicle during fabrication, inspection and shipping, and is usable to facilitate mounting of the pellicle to the photomask; (4) to provide an optical pellicle holder which is simple in construction, and which removably holds an optical pellicle such that mounting to and removal from the holder is a simple procedure which can be performed by one having little training or skill; (5) the development of a pellicle handling apparatus having an integral construction and which can be easily cleaned prior to use with an optical pellicle; (6) to provide an optical pellicle mounting apparatus which is reusable after a simple cleaning operation; (7) to provide a system for handling an optical pellicle which can be easily adapted to a wide variety of shapes and sizes of pellicles; and (8) to provide a pellicle handling system which protects the pellicle during packaging and shipping.